While padlocks serve many useful purposes with respect to preventing theft, vandalism or tresspassing, certain difficulties may arise when using known prior art devices which, if frequently encountered can be both nettlesome and time consuming.
Considering padlocks which are key operated, most commercially available padlocks are operated through a series of pins which are spring biased to enable a key. The lock mechanism itself may also include spring blasing to removeably connect the lock shackle to the main body of the lock. Under ideal circumstances, these lock provide durable and efficient service, but ideal circumstances are not always the rule, but rather the exception.
When the lock is exposed to inclement weather and/or is exposed to hostile environments such as corrosive salts or other contaminants, the lock mechanism is frequently disabled. For example, lock mechanisms frequently collect condensation which, when frozen, disable the lock. Alternatively, salt commonly used to prevent highway icing can cause corrosion and rust when it enters the lock having an adverse effect on the lock operating mechanism. Other contaminants such as soot, dust or other particulate matter can also adversely effect reliable operation of the lock.
Changes also occur in many locks as a function of time. Many locks use spring biasing and over a period of time, the spring may lose its originally engineered value. Loss of lubrication as a function of time will cause parts which once moved freely to become frozen.
These problems are magnified enormously when one has in his care and custody a plurality of locks to which one must gain access. Apart from the difficulties associated with matching one key for each lock, or more simply one master key for a series of locks, failure of the lock itself is a surprisingly common occurance. One expeditious method of overcoming a failed lock is to use bolt cutters, but obviously the lock must thereafter be replaced which would be a needless expenditure if the lock continued to work reliably.
Assume that a utility company protects access to certain power transmission equipment not only from thieves, vandals, and trespassers but also from the possibilities of tort liability. The number of locks in use grows to substantial levels, and the need for access to electrical equipment, such as during a power failure places a premium on the utility company's representative to effect repairs expeditiously. The common solution therefore, is to replace an old malfunctioning lock with a new one.
The following patents reflect the state of the art of which applicant is aware insofar as they appear relevant to the patent process. In addition, these patents are cited in direct response to applicant's acknowledged duty to disclose prior art.
______________________________________ INVENTOR(S) PATENT NUMBER ______________________________________ Bindari 4,085,600 Bottone 1,384,590 Shwayder, et al 4,064,716 Szlakman 4,038,845 Williams 1,718,723 Wiloch 1,424,543 ______________________________________
Wiloch makes it known to provide a padlock in which a screw plug is threaded for engagement with threads 5 of barrel 1 to allow a pin 8 to engage a shackle bolt. For operation, this patent provides a spring pressed plunger 19 which shows the difficulty of all other known spring biased lock mechanisms discussed hereinabove.
Similarly, the patent to Williams provides a padlock in which it is known to provide a spring F for use in selective engagement of the shackle with respect to the padlock body.
Szlakman provides a security appuratus in which the active elements are spring biased (FIG. 5, reference numeral 111).
The remaining citations commonly share double contact locking features in which a tubular shaft having cutaway portions is rotated within a lock body to selectively engage notches on either of the shackle legs. The lock mechanism is substantially in the same place as the plane of the shackle.